The devices and methods currently used for conveying fluids of the multiphase type through pipes generally combine a pump adapted for delivering a multiphase fluid consisting of at least one liquid phase and one gas phase whose volumetric ratio varies within relatively narrow limits. One is therefore obliged to use in combination a device making it possible to homogenize the fluid and thus to obtain a fluid whose volumetric ratio GLRa at the suction inlet has a value compatible with the features of the suction, which requires bulky equipments and costly investments.
French patent FR-2,642,539 mentions a known device comprising a surge drum allowing the composition fluctuations of a multiphase flow to be regulated and damped, and thus the allowable variations of the volumetric ratio of the pumped effluents may be widened within certain limits. This device or surge drum fulfils its purpose well in most cases. However, it sometimes happens that it becomes inoperative for damping the gas pockets and the oil plugs succeeding one another unforeseeably.
Moreover, pumping devices known in the prior art are not designed for taking into account the flow fluctuations of wells and the pressure drops undergone during transfers. The flow rate of the well therefore closely depends on the flow rate of the pumps used. The production capacities of wells may thus be substantially decreased.
French patent application 91/16,230 describes a method and a device for obtaining at the pump outlet a flow rate which varies like the flow rate of the well over a large variation range, by regulating the rotating speed. Determination of the rotating speed is achieved by means of parameters fluctuating upstream and downstream. These parameters may however be incompatible with the operating range of the pump; conveyance of the effluents to the terminal sometimes requires a pump outlet pressure which cannot be reached if it is merely run at the speed which can be calculated from the effective GLR value.
The operating range of the pump is defined by the parameter variation range within which the pump works properly.